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Receiving Faxes on a SIP-Trunk


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We need a solution for those customers who intent to exchange from traditional PBX to SIP-PBX and want to benefit from the saving of SIP-Trunking.

 

- Receiving of Faxes is essential

- Faxnumbers are some extension numbers of the trunk, therefore one single Trunk-registration for the whole external communication (phone and fax). No possibility to divert fax-numbers for separate registration or remain them on PSTN-Lines

(Example: 4885-0 (Telephone Switchboard) 4885-112 (Phone Extension) 4885-129 (Fax Extension). Trunk registered: 4885)

- No PSTN available, No PSTN-Gateway applicable

- SIP-Trunk Provider guarantee to support T.38 (QSC AG - Germany)

 

We absolutely do not understand, how to switch to T.38. Of course, it should depend on the DDI called (Fax-Extensions).

 

- How to setup the pbx in such a way, that certain Extensions (example above: 129) are communicating only T.38?

- We tried to setup Exchange 2007 for receiving faxes, but we only get voicemails with the "fax-beep". Is there a possibility, to force to T.38 at Exchange?

- As a workaround: We tried to forward all fax-calls to a complete different fax-numer on a seperate PSTN-Line. No way. The whole communication goes through the pbx instead of being rerouted from the SIP-Provider directly to the 3rd-pty PSTN-Fax-Machine. Any possibility to deflect the call out of the pbx?

- Does anyone know a 3rd-pty Software to setup between the SIP-Provider and pbxnsip which is able to detect and handles Faxes and divert such calls away from the pbx?

 

Any idea, hint or workaround? :( Without a solution we seem to be incapable to sell pbxnsip.

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We need a solution for those customers who intent to exchange from traditional PBX to SIP-PBX and want to benefit from the saving of SIP-Trunking.

 

- Receiving of Faxes is essential

- Faxnumbers are some extension numbers of the trunk, therefore one single Trunk-registration for the whole external communication (phone and fax). No possibility to divert fax-numbers for separate registration or remain them on PSTN-Lines

(Example: 4885-0 (Telephone Switchboard) 4885-112 (Phone Extension) 4885-129 (Fax Extension). Trunk registered: 4885)

- No PSTN available, No PSTN-Gateway applicable

- SIP-Trunk Provider guarantee to support T.38 (QSC AG - Germany)

 

We absolutely do not understand, how to switch to T.38. Of course, it should depend on the DDI called (Fax-Extensions).

 

- How to setup the pbx in such a way, that certain Extensions (example above: 129) are communicating only T.38?

- We tried to setup Exchange 2007 for receiving faxes, but we only get voicemails with the "fax-beep". Is there a possibility, to force to T.38 at Exchange?

- As a workaround: We tried to forward all fax-calls to a complete different fax-numer on a seperate PSTN-Line. No way. The whole communication goes through the pbx instead of being rerouted from the SIP-Provider directly to the 3rd-pty PSTN-Fax-Machine. Any possibility to deflect the call out of the pbx?

- Does anyone know a 3rd-pty Software to setup between the SIP-Provider and pbxnsip which is able to detect and handles Faxes and divert such calls away from the pbx?

 

Any idea, hint or workaround? :( Without a solution we seem to be incapable to sell pbxnsip.

 

First of all, check out http://wiki.pbxnsip.com/index.php/FAX.

 

If the service provider supports T.38 then that's a good start. But both ends need to support T.38. Fortunately, most SIP ATA support T.38 today.

 

Exchange is a difficult topic. I know some people got it working; but it is not easy.

 

There is also another post of available FAX software (see http://forum.pbxnsip.com/index.php?showtopic=1316). It is also worth a try.

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  • 2 weeks later...
First of all, check out http://wiki.pbxnsip.com/index.php/FAX.

 

If the service provider supports T.38 then that's a good start. But both ends need to support T.38. Fortunately, most SIP ATA support T.38 today.

 

Exchange is a difficult topic. I know some people got it working; but it is not easy.

 

There is also another post of available FAX software (see http://forum.pbxnsip.com/index.php?showtopic=1316). It is also worth a try.

Sorry for the delayed feedback. I didn't got informed about your answer and stumled today over it. Let me ask you something:

 

As the service provider does support T.38 by contract and the ATA definitely supports T.38 I'm searching the problem in the matter described at our WIKI:

 

As soon as the receiver detects that the sender wants to send a fax, it tries to re-negotiate the used codec to T.38. With this change comes a change of the used ports, as the T.38 actually does not even use RTP.

 

I do see that the AA detects the CNG Tone and "dial" the F which cause ringing the Fax ATA. But where (which log level / which messages to track) to check if the re-negotiaton to codec T.38 and change of the used ports happened or failed? Any special settings on the PBX necessary?

 

Again, in the list of codecs I do not find T.38 but this seems to be normal, isn't it?

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Sorry for the delayed feedback. I didn't got informed about your answer and stumled today over it. Let me ask you something:

 

As the service provider does support T.38 by contract and the ATA definitely supports T.38 I'm searching the problem in the matter described at our WIKI:

 

As soon as the receiver detects that the sender wants to send a fax, it tries to re-negotiate the used codec to T.38. With this change comes a change of the used ports, as the T.38 actually does not even use RTP.

 

I do see that the AA detects the CNG Tone and "dial" the F which cause ringing the Fax ATA. But where (which log level / which messages to track) to check if the re-negotiaton to codec T.38 and change of the used ports happened or failed? Any special settings on the PBX necessary?

 

Again, in the list of codecs I do not find T.38 but this seems to be normal, isn't it?

 

You will see a SIP message (typically a INVITE) coming from the ATA into the PBX. If that message that does not appear, check the configuration of the ATA, maybe you need to turn T.38 on. There is no setting on the PBX for that, everything happens automatically.

 

T.38 is not a codec, at least not for the PBX. It is like video, gaming or whatever you want to send through an established session on the PBX. The PBX does not even know it's FAX. BTW that's why you can also turn on a camera on - once you have an audio connection established.

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  • 4 weeks later...
- We tried to setup Exchange 2007 for receiving faxes, but we only get voicemails with the "fax-beep". Is there a possibility, to force to T.38 at Exchange?

 

enable inband detection in exchange (google it)

 

linksys 2102 work very well

 

netsatisfaction works well (expensive)

 

callweaver works well (free open source but have fun configuring it)

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  • 1 month later...

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